Two-stage hypochlorite bleaching of olefin sulfonate detergents

ABSTRACT

AN IMPROVED PROCESS FOR THE REDUCTION OF COLOR IN DETERGENT RANGE OLEFIN SULFONATES BY THE USE OF TWO TEMPERATURE STAGES AND HYPOCHLORITE BLEACH.

3,634,287 TWO-STAGE HYPOCHLORITE BLEACHING F OLEFIN SULFQNATE DE'I'ERGENTS Gar Lok Woo, Tiburon, Calif, assignor to Chevron Research Company, San Francisco, Calif. No Drawing. Filed Oct. 21, 1968, Ser. No. 769,386 Int. Cl. B01f 17/02 US. Cl. 252353 11 Claims ABSTRACT OF THE DISCLOSURE An improved process for the reduction of color in detergent range olefin sulfonates by the use of two temperature stages and hypochlorite bleach.

This invention relates to a process for the reduction of color in olefin sulfonates in a treatment employing hypochlorite bleach. More particularly it relates to an improved process for color reduction of sulfur trioxide-olefinic hydrocarbon derived sulfonates by the use of two temperature stages in the bleaching process.

It is known to produce sulfonates by the reaction of sulfur trioxide with detergent range olefinic hydrocarbons (see for example US. 2,061,619, US. 2,061,620 and US. 2,094,451) under mild conditions. It is known that in these reactions much undesirable color is concurrently produced and that an appreciable measure of color reduction can be achieved by treatment of the product with hypochlorite bleach (see for example British Pat. 983,056). While the conventional bleaching treatment does improve the olefin sulfonates, the result still leaves much to be desired because the color of the product is in general inferior, for example, to that of alkyl benzenesulfonate detergents long known and accepted by the trade.

It has now been found that the color reduction of substantially neutralized aqueous olefin sulfonate solutions achieved by the addition of hypochlorite bleach and heating is substantially improved when the heating is effected by the use of two temperature stages, the first of which is a relatively high temperature of from about 45 to 90 C., which in the treatment is maintained for a period of about 30 to 90 minutes, and the second of which is a moderate temperature of from about 15 to 35 C., which is maintained for a period of from about 5 to 100 hours. The cooling of the solution from the high temperature range to the moderate temperature range may be accomplished over a period of less than three hours but for best results should be promptly efiected, i.e., during a period of less than 30 minutes. i

In the bleaching reaction, heating of the sulfonate at the upper temperature range for a longer period of time in a single stage does not yield the improved result obtained in the present process employing two temperature stages. After prolonged time at elevated temperatures, color reversions occur which are not experienced provided that the temperature is reduced sufiiciently at or before the time the color reversion commences. At the reduced temperature, surprisingly, the bleaching action has been found to continue without a color reversion in What appears to be a delayed bleaching action at low temperatures. It is clear that several concurrent and possibly subsequent reactions are involved in the bleaching operation.

By definition as used herein by a detergent range olefinic hydrocarbon is meant a hydrocarbon which contains a single carbon-carbon double bond and is otherwise saturated and which contains at least 8 and less than 25 carbon atoms.

By substantial neutralization as used herein is meant by definition the addition of sufiicient sodium hydroxide,

carbonate, oxide or the equivalent inorganic acid-bindingalkali or mixtures thereof to a sulfur trioxide-olefinic hydrocarbon reaction product to adjust the pH of the mixture to a value in the range above 5 and sufiicient to yield, after neutralization and hydrolysis, a pH of the resulting mixture in the range 5 to 12. Preferably this pH value is in the range above 7, and more preferably is in the range 811. In general the amount of alkali which will be satisfactory for the above neutralization will be in the range 0.8 to 1.5 equivalents (acid-base) per mol of sulfur trioxide consumed in preparing the sulfonate.

By the term mild sulfur trioxide sulfonation conditions is meant by definition the reaction of sulfur trioxide with an olefinic hydrocarbon in the liquid phase at a temperature in the range 0 C. to 100 C. in which the sulfur trioxide is diluted prior to its introduction into the liquid phase by an inert liquid or inert gas diluent, the concentration of the sulfur trioxide in the resulting mixture being in the range 0.5 to 20 volume percent, and in which for each mol of olefin from about 0.8 to 1.3 mols of sulfur trioxide is used. Air or nitrogen are preferred inert gaseous diluents. The preferred sulfonation temperature is in the range 20 to 50 C.

In a preferred embodiment of the invention sodium hypochlorite is added to a substantially neutralized (pH -7-11) aqueous sulfonate mixture obtained from the reaction of an n-C C -a1kene-1 molecular mixture with sulfur trioxide under mild sulfonation conditions. For each 100 parts of the sulfonate 3 parts by weight of sodium hypochlorite is added to the mixture which is then heated to 85 C. for a period of 40-80 minutes. Thereafter the reaction mixture is cooled during a period of less than 30 minutes by a suitable means to 20-25 C. and maintained at this temperature for a period of 5-10 hours. Excess bleaching agent is then destroyed at the end of the second bleaching step. This may be accomplished by adding a reducing agent, e.g. sodium bisulfite. Thereafter the bleached olefin sulfonate is ready for the succeeding processing stage which is ordinarily a concentration stage and/ or a spray drying stage for the recovery of the detergent active.

The color of detergent range olefinic hydrocarbon sul fonates in general is improved by the present process. The sulfonates containing 10 to 22 carbon atoms in the molecule, preferably 12 to 20 carbon atoms are preferred feeds for the process. Molecular mixtures are included in the foregoing. All molecular types, including straight chain, branched chain, cycloaliphatic and combinations thereof are satisfactory olefin sulfonate feeds. Both internal and terminal olefinic hydrocarbons are satisfactory.

Representative olefin-sulfonate feeds for the present process include those obtained from C -C cracked wax a-olefins, as well as individual molecular range fractions thereof, C -C -u-olefins, C -C internal n-olefins, C C internal n-olefins; branched chain alkenes such as 5- methyl-l-hexadecene and the like methyl substituted nalkenes; other olefins such as cyclooctene, cyclododecene, vinylcyclohexane, dodecene 2, hexadecene-4, terpines, eicosene-l, nonene-l, octadecene-S, 4-methylcyclooctene, hendecene-2, n-octene l, n-dodecene-Z, tetracosene-l, hexadecene-4, 2,2-dimethylpe'ntadecene-6, n-propylcyclohexene-3 and the like, partially isomerized n-u-olefin, i.e., mainly n-alkene-Zs, and the like monoolefinic, non-aromatic hydrocarbons.

Minor amounts of inert impurities such as saturated hydrocarbons may be present in the olefinic hydrocarbon precursor of the subject olefin sulfonates. Similarly the presence of minor amounts (less than 50 weight percent) of alkylbenzene sulfonate detergent in the olefin sulfonate does not interfere, and possibly may be advantageous, with the instant bleaching process.

The time-temperature relationships for both steps of re' instant bleaching process are conventional. That is, as re temperature is increased, shorter reaction times are :quired. Thus for the time-temperature range couples isclosed above, the shorter times correspond to the highr temperatures in each instance.

The hydrochlorite bleach used in the invention is prefrably sodium hypochlorite although alkali metal and lkaline earth metal hypochlorites may be used. The sodim bleach is an article of commerce and least costly. On 1e other hand, the alkaline earth bleaches, such as the alcium salt, can be used but they are less desirable by aason of the unfavorable solubility parameter.

The amount of bleach relative to the sulfonate which desirably used varies, depending: (1) upon the intensity f the color of the sulfonate; (2) the particular bleach to e used; and (3) in lesser degree, the temperature to be rnployed. In general, a satisfactory amount is in the ange from about 0.25 to 5 parts (weight) per 100 parts weight) of the sulfonate. Larger relative amounts, for xample 100 parts of bleach, may be used without subtantial adverse effects, but in general such use is unsonomical, in addition the excess hypochlorite introduces )dium chloride into the product.

The subject olefin sulfonates are generally neutralized nd hydrolyzed utilizing aqueous sodium hydroxide or the quivalent. Aqueous solutions are therefore preferred for 1e bleaching. However, polar solvents relatively stable the bleach may also be used such as aqueous alcohol alutions, and the like.

The concentration of the sulfonate in the bleaching )lution may vary widely. As a practical matter, at least weight percent solution is desirably employed. All of 1e sulfonate need not be in solution for the bleaching. hus bleaching is effective where an aqueous slurry of the llfonate is used. For mechanical and economical reasons, est results in general follow from the use of aqueous slutions containing from about weight percent up to ie saturation value, i.e., usually in the range 5065 eight percent, of the sulfonate.

The pH of the reaction mixture during the bleaching eaction may be neutral or basic and preferably above The bleaching may be effected concurrently with hyrolysis.

The following examples further illustrate the inven- In the examples to follow representative preparations Examples 1 and 8) of detergent range sulfonates suitable or use in the instance process are described; and in the alance of the examples portions are treated as described. he color of the treated and untreated solutions was dezrmined by the use of a Klett-Summerson Photoelectric Iolorimeter using aqueous sulfonate solutions containing .ve percent (weight) of the olefin sulfonate.

EXAMPLE 1 Representative preparation of alpha olefin sulfonate feed for bleaching The reactor used for this sulfonation consisted of a ontinuous falling film-type unit in the form of a vertical ater jacketed tube. Both the olefin and the SO -air mix- 1re were introduced at the top of the reactor and flowed oncurrently down the reactor. At the bottom the sul- Jnated product was separated from the air stream.

The feed stock for this example was a l-olefin blend aving the following composition by weight: 1% tetraecene, 27% pentadecene, 29% hexadecene, 28% heptaecene, 14% octadecene, and 1% nonadecene. This mateial was charged to the above described apparatus at a ate of 306 pounds/ hour. At the same time 124.2 pounds/ our of S0 diluted with :air to 3% by volume was introuced into the top of the reactor. The apparatus was ooled with water in order to maintain the temperature of 1c product within the range of 43-46 C. Under these conditions the average residence time was less than two minutes.

After passing out of the reactor the air-free sulfonateed product was mixed with 612 pounds/hour of 11.2% aqueous caustic. The resulting slurry was hydrolyzed by heating at 145-150 C. in a tubular reactor at an average residence time of 30 minutes. In this way 463 pounds/hour of olefin sulfonate was obtained as a 45% aqueous solution having a pH of 10.8. The yield was 95.5%.

A portion of this product was analyzed and shown to be made up of the sodium salts of alkene sulfonic acids, hydroxyalkane sulfonic acids, with a minor proportion of disulfonic acids.

EXAMPLE 2 A portion of the product from Example 1 was diluted with water to yield a 5 percent (weight) solution (sample 1). This solution had a color value of 680 Klett units (40 mm. cell).

-A second portion of the product from Example 1 was diluted with water to yield a 25 percent (weight) solution and 600 grams of solution of this concentration were charged to a glass reaction vessel.

The reactor and contents were heated up to about 83 C. at which time 38.2 grams of aqueous sodium hypochlorite (11.8% hypochlorite by weight) were added. The mixture was maintained at :2" C. for one hour with stirring after which time a 21.3 gram sample was removed from the flask. Distilled water was added to cool and dilute the solution to a 5 weight percent concentration of olefin sulfonate active. The resulting solution Was then filtered. The color of the dilute solution was measured in a 40 mm. colorimeter cell and found to be 132 Klett units.

EXAMPLE 3 One-half of the solution remaining after removal of the sample in Example 1 was maintained at 80i2 C. for 5 additional hours and the color value determined ash in Example 1. It was 217.

EXAMPLES 4-7 In the manner as described above and for the periods stated in the following table additional color values were determined.

TABLE.COL0 R VALUES FO R BLEACHED 1 OLEFIN SULFONATES Treatment First stage Second stage Temp., Temp, Color Sample No C. Hours 0. Hours Klett 1 Bleaching with 3% 2 No treatment.

XAMPLE 8 The feed stock for this sulfonation was a l-olefin mixture having the same composition as in Example 1. The reactor was similar to that of Example 1, except smaller in size. The l-olefin mixture was fed to the sulfonates at a rate of 4.37 gram/min. At the same time, 1.88 gram/ min. of S0 (diluted with nitrogen to 3% by volume) was introduced into the top of the reactor. The temperature was maintained at 80 C. Under these conditions the average residence time was less than two minutes.

After passing out of the reactor, the sulfonates product was collected in 30-minute portions. These were each mixed with 353 grams of 8% aqueous sodium hydroxide. The resulting slurry was hydrolyzed as in Example 1. After hydrolysis the product was diluted with water to an 18.1% concentration. A portion of this solution was further diluted to 5% (weight) and filtered. The color of this solution in a 20 mm. cell was 760 Klett units.

EXAMPLE 9 EXAMPLE 10 The dilute and treated solution of Example 9 was cooled and stored in a glass flask for 9 days at 22 to 25 C. At the end of this time the color (40 mm. cell) was 137 Klett units.

EXAMPLE 11 Another batch of olefin sulfonate was prepared by the procedure of Example 8. A portion of this material was diluted to produce a 25% solution. It was then bleached in the manner of Example 9. At the end of one hour the bleached solution was cooled to room temperature. Portions of this solution were periodically removed, diluted to 5% and analyzed for color. The color values for the 5% solution were as follows.

Time (days): Color 1 O 228 1 155 2 115 3 95 6 93 1 Klett units in a 20 mm. cell.

EXAMPLE 12 A portion of the crude sulfonate of Example 11 was bleached as before except that the temperature was maintained at 80i2 C. for one hour and then cooled to room temperature, i.e. 2022 C. and maintained at this temperature. The color values for the 5% solutions were as follows:

Time (days): Color 1 137 1 104 2 96 3 95 1 Klett units in a 20 mm. cell.

The foregoing examples demonstrate that improved reduction of color in the hypochlorite bleaching of olefin sulfonates can be obtained provided that two temperature stages are employed in the manner described above.

What is claimed is:

1. In the reduction of the color of an aqueous sulfonate by adding hypochlorite bleach and heating the resulting mixture, said sulfonate having been obtained by the reaction of sulfur trioxide with a detergent range olefinic hydrocarbon under mild sulfur trioxide sulfonation conditions followed by substantial neutralization with strong alkali, and wherein for each 100 parts by weight of the sulfonate from about 0.25 to 5 parts of the bleach is present in the mixture, the improvement which comprises heating said mixture to an elevated temperature in the range from about 45 to 90 C. for a period in the range from 30 to 90 minutes, thereafter cooling said heated mixture to a moderate temperature in the range from about 15 to 35 C. and maintaining said lower temperature for a period in the range from about 5 to 100 hours, said cooling from the elevated range to the moderate range being eifected in a period of less than 5 hours.

2. The process as in claim 1 further characterized in that said elevated temperature range is from about to 85 C., said lower temperature is in the range 20 to 25 C., said period at the elevated temperature is in the range 40 to minutes, said period at the lower temperature is in the range 5 to 10 hours, and said cooling is effected during a period of time which is less than 30 minutes.

3. The process as in claim 2 further characterized in that said olefin sulfonate is selected from the group consisting of n-C -C -alkene sulfonates and mixtures thereof.

4. The process as in claim 3 further characterized in that said alkene sulfonate is an internal sulfonate.

5. The process as in claim 3 further characterized in that said alkene sulfonate is an internal olefin sulfonate.

6. The process as in claim 1 further characterized in that said neutralization is to a pH value in the range from about 7 to 11.

7. In the reduction of the color of an aqueous sulfonate by adding hyprochlorite bleach and heating the resulting mixture, said sulfonate having been obtained by the action of sulfur trioxide with a detergent range olefinic hydrocarbon under mild sulfur trioxide sulfonation conditions followed by substantial neutralization with strong alkali, and wherein for each 100 parts by weight of the sulfonate about 3 parts of the bleach is present in the mix-,

ture, the improvement which comprises heating said mixture to an elevated temperature in the range from about 75 to C. for a period in the range from 40 to 80 min. utes, thereafter cooling said heated mixture to a moderate temperature in the range from about 20 to 25 C. and maintaining said lower temperature for a period in the range from about 5 to 10 hours, said cooling from the elevated range to the moderate range being effected in a period of less than 30 minutes.

8. The process as in claim 7 further characterized in that said olefin sulfonate is selected from the group consisting of terminal n-c -C -alkene sulfonates, of internal n-C -c -alkene sulfonates, and of molecular mixtures thereof.

9. The process as in claim 7 further characterized in that said neutralization is to a pH value in the range from about 7 to 11.

10. The process as in claim 7 further characterized in that said elevated temperature is about 80 C. and said moderate temperature is about 2025 C.

11. The process as in claim 7 further characterized in that said elevated temperature is about 53 C. and said moderate temperature is about 20-25 C.

References Cited UNITED STATES PATENTS 3,424,694 1/1969 Stein et al. 252161 JOHN D. WELSH, Primary Examiner US. Cl. X.R. 260-513; 252- 

